Abstract
Introduction: The oxytocin challenge test (OCT) used to be one of the most important tools in assessing fetal well-being before ultrasonography became prevalent. We show that, after modifying the classification of the results and the intervention algorithm, OCT can still be a useful tool in present-day obstetrics. Material and methods: The study included 318 OCTs performed in patients admitted to our department from 2010 to 2012. A modified classification of test results was introduced, dividing the results in four groups: I-negative, II-positive, III-non-diagnostic and type IV (fetal tachycardia or increased variability). The purpose of the study was to evaluate the clinical significance of OCT in assessing intrauterinal fetal well-being and predicting the necessity for ending the pregnancy. Results: A significant difference (p < 0.001) in the delivery method and the indications for cesarean sections (CS) was found between negative and positive OCT results. CS indicated by an abnormal fetal heart rate (FHR) pattern had to be performed in 40% of cases with positive OCT results, having constituted 84.6% of all CSs in this group. After negative OCTs, 12.8% pregnancies were ended by CS from FHR indications (62.3% of all the indications). Conclusions: A positive OCT result can be a valuable predictor of an abnormal fetal heart rate pattern after the test and during the delivery, as well as a higher probability of a CS from cardiotocography (CTG) indications, with positive predictive value (PPV) 0.50 and negative predictive value (NPV) 0.85.
Highlights
The oxytocin challenge test (OCT) used to be one of the most important tools in assessing fetal well-being before ultrasonography became prevalent
The indications for OCT were divided into the following categories: intrauterine fetal growth restriction (IUGR), pre-pregnancy medical history, pregnancy-induced medical conditions, adverse obstetric history, pregnancy after term, any previous suspicious CTG tracings, abnormal fetal movements and increased or reduced amniotic fluid volume
An increased number of positive results was observed in patients qualified to OCT because of IUGR (38.3%) and suspicious CTG recordings before the test (48.4%)
Summary
The oxytocin challenge test (OCT) used to be one of the most important tools in assessing fetal well-being before ultrasonography became prevalent. A modified classification of test results was introduced, dividing the results in four groups: I-negative, II-positive, III-non-diagnostic and type IV (fetal tachycardia or increased variability). CS indicated by an abnormal fetal heart rate (FHR) pattern had to be performed in 40% of cases with positive OCT results, having constituted 84.6% of all CSs in this group. According to the Society of Obstetricians and Gynecologists of Canada Guideline, there is still a place for OCT in a modern obstetric unit It should be considered in case of pathological or suspicious non-stress test (NST) to evaluate uteroplacental function during contractions in patients primarily qualified for a vaginal delivery [3]. As OCT has been abandoned in many perinatal centers, in our study we wanted to present the still-existing utility of OCT in modern obstetrics, with an additional upgrade in the form of a modified classification of the test results
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